Various types of hernia mesh are known. They are usually flat, wide-meshed, warp-knitted textiles made from polypropylene monofilament yarns.
Hernia meshes are normally introduced through smaller openings in the abdomen and should unfurl as easily as possible inside the abdomen. They should lie against the internal wall of the abdomen or become embedded in the intermediate layers. On the one hand, it is desirable to implant the smallest possible amount of foreign body, since it has been shown that this avoids undesirable rejection and cicatrization that are common with relatively stiff hernia meshes having a large weight per unit area. On the other hand, when hernia meshes have a low weight per unit area, i.e., such as those made from thin monofilament yarns, problems with material unfurling may occur, since these types of hernia meshes have a low elastic recovery and cannot unfurl easily after they have been inserted into the abdominal cavity.
To solve these problems, combined hernia meshes have been developed, which consist of a basic structure, which is usually made from a non-resorbable material, with a reinforcing structure superimposed on it, which is usually made from a resorbable material. These independent, warp-knitted structures are usually produced on single- or two-bar machines and are disclosed in EP 0 797 962 B1, EP 1 099 422 B1 and DE 199 42 611 C1, for example. The advantage of hernia meshes made from a combination of resorbable and non-resorbable yarns is that they have the required stiffness for implantation. Once they have been implanted, the resorbable yarns degrade, leaving behind the relatively lightweight, warp-knitted textile made from non-resorbable yarns. Since the composite warp-knitted textiles are made up of two independent warp-knitted textiles, which are joined together during the knitting process, an intact warp-knitted textile made from non-resorbable yarns remains after the resorbable yarns have been resorbed. However, the disadvantage of these types of composite warp-knitted textiles is that they are complicated to produce.